// 在业务代码执行之前，导入缺失的特性（垫片）

const arr = ['hello', 'world']
const ret = arr.includes('hello')
const ret2 = Object.assign({}, {
  a: 1,
  b: 2
})
console.log(ret)
console.log(ret2)


const fn = () => {
  console.log('箭头函数')
}
console.log(fn)



class Hello {

}
console.log(new Hello())

console.log(Hello)

import './world.js'